Stacked semiconductor device and method of manufacturing the same

ABSTRACT

A stacked semiconductor device includes a first semiconductor element mounted on a circuit substrate and a second semiconductor element stacked on the first semiconductor element via a spacer layer. An electrode pad of the first semiconductor element is electrically connected to a connection portion of the circuit substrate through a first metal wire. A vicinity of the end portion of the first metal wire connected to the electrode pad is in contact with an insulating protection film which covers the surface of the first semiconductor element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2007-021060 filed on Jan. 31,2007; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a stacked semiconductor device and amethod of manufacturing the same.

2. Description of the Related Art

To realize miniaturization and high-density packaging of thesemiconductor device, a stacked semiconductor device having pluralsemiconductor elements stacked and sealed in one package has alreadybeen put into practical use. In the stacked semiconductor device, theplural semiconductor elements are sequentially stacked on a circuitsubstrate such as a wiring board and a lead frame via an adhesive layer.The electrode pads of the individual semiconductor element areelectrically connected to the connection portions of the circuitsubstrate through metal wires. Such a laminated body is packaged with asealing resin to configure the stacked semiconductor device.

The above-described stacked semiconductor device has a possibility thatwhen the semiconductor elements having the same shape are stacked or asemiconductor element having a larger size is stacked on a lower andsmaller semiconductor element, the metal wires connected to the lowersemiconductor element are contacted to the upper semiconductor element.Therefore, it is important to prevent the occurrence of an insulationfailure, a short circuit or the like due to the contact of the metalwires with the upper semiconductor element. Then, a bonding method usingthe metal wires is improved in various ways to control a loop height ofthe metal wires connected to the lower semiconductor element to a lowlevel.

Known bonding methods capable of lowering the height of the wire loopinclude a connecting method (1) which forms a metal bump on an electrodepad of a semiconductor element, performs ball connection of one end ofthe metal wire to a connection portion of a circuit substrate andpressure-bonds the other end of the metal wire to the metal bump on theelectrode pad (a reverse bonding method (see JP-A 2005-328005)), and aconnecting method (2) which performs ball connection of one end of ametal wire to an electrode pad of a semiconductor element, squashes thetop portion of the ball together with a part of the metal wire, lets outthe metal wire, and pressure-bonds the other end of the metal wire tothe connection portion of the circuit substrate (see JP-A 2004-172477).

The reverse bonding method (1) can decrease the loop height incomparison with the ordinary bonding (forward bonding), but theconventional method has the height of the metal bump as an obstacle tothe further reduction of the height of the wire loop because of thepressure bonding of the metal wire to the metal bump formed on theelectrode pad of the semiconductor element. According to the bondingmethod (2), even if the ball bonded to the electrode pad of thesemiconductor element is squashed, the reduction of the height of theball is limited, and it is difficult to make the loop height of themetal wire lower than, for example, the height of about two times of thewire diameter including the ball-bonded portion.

JP-A 2005-116916 discloses that a metal wire is connected to anelectrode pad, which is formed at the vicinity of the center of asemiconductor element, by performing ball connection of one end of themetal wire to the electrode pad, the metal wire is let out in contactwith an insulating film (silicon nitride film) of the surface of thesemiconductor element so that the metal wire has an M-shaped loop (aloop shape having three bent portions), and the other end of the metalwire is connected to an external terminal by pressure bonding. Thesimple provision of the metal wire with the M-shaped loop can preventthe contact between the outer circumference of the semiconductorelement, but cannot decrease sufficiently the loop height of the metalwire.

SUMMARY OF THE INVENTION

A stacked semiconductor device according to an aspect of the presentinvention includes: a circuit substrate having an element mountingsection and a connection portion; a first semiconductor element, mountedon the element mounting section of the circuit substrate, including asemiconductor element body, a first electrode pad disposed on a surfaceof the semiconductor element body and an insulating protection filmcovering the surface while exposing the first electrode pad; a secondsemiconductor element, stacked on the first semiconductor element via aspacer layer, including a semiconductor element body and a secondelectrode pad disposed on a surface of the semiconductor element body; afirst metal wire which electrically connects the connection portion ofthe circuit substrate and the first electrode pad of the firstsemiconductor element, the first metal wire disposing to contact avicinity of its end portion connected to the first electrode pad withthe insulating protection film; and a second metal wire whichelectrically connects the connection portion of the circuit substrateand the second electrode pad of the second semiconductor element.

A manufacturing method of a stacked semiconductor device according to anaspect of the present invention includes: mounting a first semiconductorelement having an electrode pad on an element mounting section of acircuit substrate having a connection portion; forming a metal bump onthe electrode pad of the first semiconductor element; connecting a metalball formed at a first end portion of a metal wire to the connectionportion of the circuit substrate by pressure bonding; wiring the metalwire toward the electrode pad of the first semiconductor element;connecting a second end portion of the metal wire to the metal bumpformed on the electrode pad while contacting the metal wire to aninsulating protection film which is formed to cover a periphery of theelectrode pad; and stacking a second semiconductor element on the firstsemiconductor element via a spacer layer.

A manufacturing method of a stacked semiconductor device according toanother aspect of the present invention includes: mounting a firstsemiconductor element having an electrode pad on an element mountingsection of a circuit substrate having a connection portion; connecting ametal ball formed at a first end portion of a metal wire to theelectrode pad of the first semiconductor element by pressure bonding;wiring the metal wire toward the connection portion of the circuitsubstrate while contacting the metal wire to an insulating protectionfilm which is formed to cover a periphery of the electrode pad;connecting a second end portion of the metal wire to the connectionportion of the circuit substrate; and stacking a second semiconductorelement on the first semiconductor element via a spacer layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a stacked semiconductor deviceaccording to a first embodiment.

FIG. 2 is a sectional view showing a modified example of the stackedsemiconductor device shown in FIG. 1.

FIG. 3 is a sectional view showing a step of forming a metal bump on afirst electrode pad in a manufacturing process of the stackedsemiconductor device shown in FIG. 1.

FIG. 4 is a diagram showing a connecting step including a wiringoperation of a first metal wire in the manufacturing process of thestacked semiconductor device shown in FIG. 1.

FIG. 5 is a sectional view showing a step of connecting the first metalwire to the metal bump in the manufacturing process of the stackedsemiconductor device shown in FIG. 1.

FIG. 6 is a sectional view showing a modified example of the step ofconnecting the first metal wire shown in FIG. 5.

FIG. 7 is a sectional view showing a connecting operation of the metalwire to the metal bump according to another modified example of the stepof connecting the first metal wire shown in FIG. 5.

FIG. 8 is a sectional view showing a contacting operation of the metalwire to an insulating protection film according to another modifiedexample of the step of connecting the first metal wire shown in FIG. 5.

FIG. 9 is a sectional view showing a stacked semiconductor deviceaccording to a second embodiment.

FIG. 10 is a sectional view showing a step of ball connection of thefirst metal wire onto a first electrode pad in a manufacturing processof the stacked semiconductor device shown in FIG. 9.

FIG. 11 is a sectional view showing a metal ball connecting operation ina modified example of the step of ball connection of the first metalwire shown in FIG. 10.

FIG. 12 is a sectional view showing the contacting operation of themetal wire to an insulating protection film in the modified example ofthe step of ball connection of the first metal wire shown in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

Modes of conducting the present invention will be described below withreference to the drawings. FIG. 1 is a sectional view showing thestructure of a stacked semiconductor device having a stacked multichippackage structure according to a first embodiment of the invention. Astacked semiconductor device 1 shown in FIG. 1 includes a wiring board 2as an element mounting circuit substrate. The wiring board 2 can mountthereon a semiconductor element and may have a wiring network which isdisposed on the surface and interior.

As the substrate configuring the wiring board 2, an insulating substratesuch as a resin substrate, a ceramic substrate or a glass substrate, ora semiconductor substrate or the like can be applied. As the wiringboard 2 applying the resin substrate, a general multilayer copper-cladlaminate (multilayer-printed board) is used. The under surface of thewiring board 2 is provided with external connection terminals 3 such assolder bumps. The top surface of the wiring board 2 is provided with anelement mounting section 2 a, and connection pads 4 which areelectrically connected via the external connection terminals 3 and awiring network (not shown) are disposed along the periphery of theelement mounting section 2 a. The connection pads 4 become connectionportions when wire bonding.

A first semiconductor element 5 is adhered to the element mountingsection 2 a of the wiring board 2 via a first adhesive layer 6. For thefirst adhesive layer 6, a general die-attach film or the like is used.The first semiconductor element 5 has an element body 5 a having acircuit including transistors formed and first electrode pads 7 disposedon the surface (top surface) of the element body 5 a. The top surface ofthe first semiconductor element 5 is covered with an insulatingprotection film 8 which is disposed to expose the first electrode pads7. For the insulating protection film 8, a passivation layer formed ofan SiO_(x) layer, an SiNe layer or the like and an insulation resinlayer such as a polyimide resin layer which is additionally formedthereon are applied.

The first electrode pads 7 are electrically connected to the connectionpads 4 of the wiring board 2 through first metal wires 9 such as Auwires. In FIG. 1, the first metal wires 9 are bonded by reverse bonding.In other words, metal bumps 10 are formed on the first electrode pads 7.One end (first end) of the first metal wire 9 is ball-connected to theconnection pad 4 of the wiring board 2, and the other end (second end)is connected to the metal bump 10 formed on the first electrode pad 7. Avicinity of end portion (element-side end) of first metal wire 9connected to the first electrode pad 7 is in contact with the insulatingprotection film 8 as described later in detail.

On the first semiconductor element 5, a second semiconductor element 11is adhered via a second adhesive layer 12. The second semiconductorelement 11 has the same shape as the first semiconductor element 5 or ashape which is at least partly larger than the first semiconductorelement 5. The second adhesive layer 12 is softened or fused at leastpartly at the bonding temperature to adhere the first semiconductorelement 5 and the second semiconductor element 11 while taking thereinthe element-side end (connecting-side end portion with the firstsemiconductor element 5) of the first metal wire 9. An adhesive formedof an insulation resin is used for the second adhesive layer 12 tosecure the insulation of the first metal wire 9.

The element-side end of the first metal wire 9 is buried in the secondadhesive layer 12 to prevent contact with the second semiconductorelement 11. Thus, the second adhesive layer 12 has a function as aspacer layer in addition to the function as an adhesive layer. Thespacer layer may be configured of a chip smaller than the semiconductorelements 5, 11. In such a case, the element-side end of the first metalwire 9 is disposed in a space formed by virtue of the spacer layerdisposed between the semiconductor elements 5 and 11 and prevented frombeing contacted with the second semiconductor element 11.

In the stacked semiconductor device 1 shown in FIG. 1, the first metalwire 9 is separated from the under surface of the second semiconductorelement 11 based on the thickness (the space between the firstsemiconductor element 5 and the second semiconductor element 11) of thesecond adhesive layer 12. To obtain the function as the spacer layer,the thickness of the second adhesive layer 12 is desirably 30 μm ormore, and more desirably 50 μm or more. Meanwhile, if the secondadhesive layer 12 is excessively thick, the stacked semiconductor device1 is inhibited from being made thin, so that the thickness of the secondadhesive layer 12 is desirably 100 μm or less, and more desirably 80 μmor less.

In order to prevent the contact between the element-side end of thefirst metal wire 9 and the second semiconductor element 11 moresecurely, the second adhesive layer 12 may have a first resin layer(adhesive layer) which is softened or fused at the adhering temperatureand a second resin layer (insulation layer) which retains the layershape at the adhering temperature. The element-side end of the firstmetal wire 9 is taken into the first resin layer, which is disposed onthe side of the first semiconductor element 5, and its contact with thesecond semiconductor element 11 is prevented by the second resin layerwhich is disposed on the side of the second semiconductor element 11.The first resin layer desirably has a thickness of about 30 to 70 μm.The second resin layer desirably has a thickness of 5 to 15 μm.

Since the first metal wire 9 is disposed in the second adhesive layer12, it is necessary that the loop height (specifically, the height abovethe first semiconductor element 5) is made lower than the thickness ofthe second adhesive layer 12. For example, in a case where the secondadhesive layer 12 has a thickness of 60 μm, it is necessary that thefirst metal wire 9 has a height of 50 μm or less on the firstsemiconductor element 5. In a case where the adhesive layer 12 having atwo-layer structure is applied, it is necessary that the first metalwire 9 has a height of 50 μm or less because the second resin layer(insulation layer) has a thickness of about 10 μm.

To realize the height of the first metal wire 9 described above, thefirst embodiment applies reverse bonding for connection of the firstmetal wire 9, and contacting the vicinity of the element-side end of thefirst metal wire 9 to the insulating protection film 8. The loop heightis decreased by applying the reverse bonding, and the first metal wire 9is contacted to the insulating protection film 8 to perform wiring.Thus, it possible to decrease the height of the first metal wire 9 onthe first semiconductor element 5 satisfactorily. For example, where theAu wire having a diameter of 25 μm is applied, the height of the firstmetal wire 9 on the first semiconductor element 5 can be decreased to 50μm or less, and also to a value close to the diameter of the metal wire9.

The second semiconductor element 11 adhered to the first semiconductorelement 5 has second electrode pads 13 disposed on a surface (topsurface) of an element body 11 a. The second electrode pads 13 areelectrically connected to the connection pads 4 of the wiring board 2through second metal wires 14 to which the reverse bonding is applied.Metal bumps 15 are formed on the second electrode pads 13, and one endsof the second metal wires 14 are connected to the metal bumps 15. Thesurface of the second semiconductor element 11 is covered with aninsulating protection film 16 in the same manner as the firstsemiconductor element 5.

The first and second semiconductor elements 5, 11 stacked on the wiringboard 2 are sealed with a sealing resin 17 such as an epoxy resin toconfigure the stacked semiconductor device 1 having a stacked multichippackage structure. In FIG. 1, the structure that the two semiconductorelements 5, 11 were stacked was described, but the number of stackedsemiconductor elements is not limited to the above. The number ofstacked semiconductor elements may be three or more.

FIG. 1 shows a structure that the first and second semiconductorelements 5, 11 are stacked on the wiring board 2, but the structure ofthe stacked semiconductor device 1 of the first embodiment is notlimited to the above. The stacked semiconductor device 1 of the firstembodiment may be a semiconductor package (such as TSOP) which has thefirst and second semiconductor elements 5, 11 stacked sequentially on alead frame 18 as shown in FIG. 2. The number of stacked semiconductorelements may be three or more.

The stacked semiconductor device 1 having the TSOP structure shown inFIG. 2 has the lead frame 18 as an element-mounting circuit substrate.The lead frame 18 has an element-mounting section 19 and lead portions20. The lead portions 20 serve as connection portions (inner leadportions) electrically connected to the first and second semiconductorelements 5, 11, which are stacked on the element-mounting section 19,and external connection terminals (outer lead portions).

The first semiconductor element 5 and the second semiconductor element11 are sequentially adhered onto the element mounting section 19 of thelead frame 18 via the first and second adhesive layers 6, 12. Theelectrode pads 7, 13 of the first and second semiconductor elements 5,11 and the lead portion 20 of the lead frame 18 are electricallyconnected through the metal wires 9, 14. The connected structure (abonding method, a mode of the element-side end, etc.) of the metal wires9, 14 is determined to be same as that of the stacked semiconductordevice 1 shown in FIG. 1. Besides, the function, structure, shape andthe like of the second adhesive layer 12 are also same as those of thestacked semiconductor device 1 shown in FIG. 1.

A connecting step of the first metal wire 9 of the stacked semiconductordevice 1 of the first embodiment is described in detail with referenceto FIG. 3 through FIG. 8. First, the metal bump 10 is formed on thefirst electrode pad 7 before the connecting step of the first metal wire9. Specifically, a metal ball (such as an Au ball) formed at a leadingend of a metal wire such as an Au wire is press-contacted to theelectrode pad 7, and a load and ultrasonic oscillation are applied tothe metal ball to bond (pressure-bond) to the electrode pad 7.

At this time, it is desirable that a bonding tool (capillary) 22, whichsupports a metal wire 21, is moved in a direction (a direction toward afeeding direction of the metal wire viewed from the electrode pad 7)toward an end portion (an end located below the metal wire) of thesemiconductor element 5 as shown in FIG. 3 to squash a metal ball 23which is bonded to the electrode pad 7. The metal ball 23 is squashed toincline toward the wire feeding direction. The step of squashing themetal ball 23 may be performed by raising once the bonding tool 22 whichhas pressure-bonded the metal ball 23 to the electrode pad 7, moving thebonding tool 22 in that state toward the end portion of thesemiconductor element 5, and lowering the bonding tool 22 to re-pressthe metal ball 23.

The height of the metal ball 23 bonded to the electrode pad 7 can bedecreased by squashing the metal ball 23 by the bonding tool 22. Theheight of the first metal wire 9 on the first semiconductor element 5can be lowered furthermore by decreasing the height of the metal ball23. Besides, the connected height of the first metal wire 9 can belowered furthermore by squashing the metal ball 23 to incline toward thewire feeding direction. Then, the bonding tool 22 is pulled up to cutoff the metal wire 21 so as to form the metal bump 10 on the electrodepad 7. The metal bump 10 has a squashed shape to incline toward the endportion (end portion located below the metal wire) of the semiconductorelement 5 through the step of squashing the metal ball 23.

As shown in FIG. 4, a metal ball (such as an Au ball) 24 is then formedat a leading end (first end) of the wire bonding metal wire (such as anAu wire) 21 and connected (ball-connected) to the connection pad 4 ofthe wiring board 2. The ball connection step is performed by applying aload and ultrasonic oscillation in the same manner as the ordinary wirebonding. Subsequently, the bonding tool 22 is moved to the above of themetal bump 10 which is formed on the electrode pad 7 while wiring byletting out the metal wire 21 from the bonding tool 22.

At that time, the bonding tool 22 is pitched downward onto theinsulating protection film 8 to connect (stitch-bond) to the metal bump10 while the metal wire 21 is in contact with the insulating protectionfilm 8 which is disposed on the periphery of the electrode pad 7 asshown in FIG. 5. The metal wire 21 is contacted onto the insulatingprotection film 8 located in a wire feeding direction when viewed fromthe metal bump 10 and connected to the metal bump 10 continuously fromthe portion contacted to the insulating protection film 8. The stitchbonding is performed by applying a load and ultrasonic oscillation inthe same manner as the ordinary wire bonding.

If the metal wire 21 is simply connected to the metal bump 10, theheight of the metal wire 21 on the semiconductor element 5 cannot bemade lower than the connection height based on the height of the metalbump 10 and also the height based on the loop shape of the metal wire 21at the time of connecting to the metal bump 10. Accordingly, in thefirst embodiment, the metal wire 21 is connected to the metal bump 10while it is kept contacted to the insulating protection film 8. In otherwords, the vicinity of the connection portion between the metal wire 21and the electrode pad 7 (specifically, the metal bump 10) is in contactwith the insulating protection film 8 located in the wire feedingdirection when viewed from the connection portion (the electrode pad 7).

Thus, it becomes possible to lower the height of the metal wire 21 onthe semiconductor element 5 by contacting the metal wire 21 to theinsulating protection film 8. Besides, the metal wire 21 is contactedonto the insulating protection film 8, which is located in the wirefeeding direction when viewed from the electrode pad 7, and connected tothe electrode pad 7 continuously from the contact portion. Thus, theheight of the metal wire 21 on the semiconductor element 5 can be lower.Specifically, the height of the metal wire 21 on the semiconductorelement 5 can be lowered to a value close to the diameter of the metalwire 21 excepting the height of the connection portion between the metalwire 21 and the metal bump 10.

The connection height of the metal wire 21 on the metal bump 10 can bemade lower by performing the squashing operation of the metal bump 10shown in FIG. 6 in addition to the squashing operation in the bondingprocess of the metal ball 23 shown in FIG. 3. In other words, after themetal wire 21 is connected to the metal bump 10, the bonding tool 22 ismoved horizontally in a direction (the center direction of thesemiconductor element 5) opposite to the wire feeding direction tofurther squash the metal bump 10. The connection height with the metalbump 10 can be made lower furthermore. The metal bump 10 is also made tohave a squashed shape which is inclined toward (toward the wire feedingdirection) the end portion of the semiconductor element 5 by thesquashing step after the connection of the metal wire 21.

The contacting operation of the metal wire 21 to the insulatingprotection film 8 may be performed after the metal wire 21 is connectedto the metal bump 10 as shown in FIG. 7 and FIG. 8. First, the wiredmetal wire 21 is connected to the metal bump 10 as shown in FIG. 7.Then, the bonding tool 22 is moved horizontally in the wire feedingdirection as shown in FIG. 8 to press the metal wire 21 to contact tothe insulating protection film 8. Thus, the metal wire 21 can becontacted to the insulating protection film 8, and it becomes possibleto lower the height of the metal wire 21. The same is also applied tothe connection height with respect to the metal bump 10.

After the connecting step (including the contacting step to theinsulating protection film 8) of the metal wire 21 to the metal bump 10is performed, the bonding tool 22 is pulled up to cut off the metal wire21. After the metal wire 21 is cut off, the end portion (second endportion) is in connection with the metal bump 10 in a state continuousfrom the portion contacted to the insulating protection film 8. Thefirst metal wire 9 is formed to electrically connect the first electrodepad 7 of the first semiconductor element 5 and the connection pad 4 ofthe wiring board 2. The application of the connecting step for the metalwire 21 enables to obtain the first metal wire 9 with its height on thefirst semiconductor element 5 lowered satisfactorily with a goodreproducibility. The first metal wire 9 does not come into contact withthe end portion (edge) of the first semiconductor element 5 by thewiring of the metal wire 21.

According to the first embodiment, the height of the first metal wire 9on the first semiconductor element 5 can be lowered satisfactorily.Thus, the element-side end of the first metal wire 9 can be finelyburied into the second adhesive layer 12 which adheres while keepingsmall the gap between the first semiconductor element 5 and the secondsemiconductor element 11. In other words, the occurrence of aninsulation failure or a short circuit because of the contact between thefirst metal wire 9 buried into the second adhesive layer 12 and thesecond semiconductor element 11 can be prevented, and the occurrence ofa connection failure which might be caused when the connection portionbetween the first metal wire 9 and the first electrode pad 7 is deformedexcessively when the second semiconductor element 11 is adhered can besuppressed.

Thus, the stacked semiconductor device 1 which is made thin by reducingthe gap between the first semiconductor element 5 and the secondsemiconductor element 11 can be provided with a good reproducibilitywhile the occurrence of an insulation failure or a short circuit becauseof the contact between the first metal wire 9 and the secondsemiconductor element 11 and the occurrence of a connection failure dueto excessive deformation of the first metal wire 9 are prevented. Inother words, the production yield, reliability and the like of the thinstacked semiconductor device 1 can be enhanced.

Then, the stacked semiconductor device according to a second embodimentof the invention is described with reference to FIG. 9. FIG. 9 is asectional view showing a structure of the stacked semiconductor devicehaving a stacked multichip package structure of the second embodiment ofthe invention. A stacked semiconductor device 30 shown in FIG. 9 has theelectrode pads 7, 13 of the first and second semiconductor elements 5,11 and the connection pads 4 of the wiring board 2 electricallyconnected through metal wires 31, 32 by forward bonding. The otherstructure is determined to be same as that of the first embodiment.

The first metal wire 31 which connects the first electrode pad 7 of thefirst semiconductor element 5 and the connection pad 4 of the wiringboard 2 has its one end (first end) ball-connected to the firstelectrode pad 7 and the other end (second end) stitch-bonded to theconnection pad 4. The vicinity of end portion (element-side end) of thefirst metal wire 31 connected to the first electrode pad 7 is incontacted with the insulating protection film 8. The second metal wire32, which connects the second electrode pad 13 of the secondsemiconductor element 11 and the connection pad 4 of the wiring board 2,also has its one end ball-connected to the second electrode pad 13 andthe other end stitch-bonded to the connection pad 4.

In the second embodiment, the first metal wire 31 which isball-connected to the first electrode pad 7 is contacted to theinsulating protection film 8 to reduce the height of the first metalwire 9 on the first semiconductor element 5. Thus, even when the forwardbonding is applied to the connecting step for the first metal wire 31,the height of the first metal wire 9 can be reduced by contacting thevicinity of the element-side end of the first metal wire 31 to theinsulating protection film 8. Thus, the stacked semiconductor device 30can be made thin and the integrity and reliability of the connectedportion of the first metal wire 31 can also be improved.

Similar to the stacked semiconductor device 1 of the first embodiment,the stacked semiconductor device 30 of the second embodiment may also bea semiconductor package (such as TSOP) which has the first and secondsemiconductor elements stacked sequentially on the lead frame. Thespecific structure of such a case is as shown in FIG. 2. The number ofstacked semiconductor elements may be three or more.

Then, a forming step (connecting step for the metal wire) for the firstmetal wire 31 of the stacked semiconductor device 30 of the secondembodiment is described in detail with reference to FIG. 10 through FIG.12. First, a metal ball (such as an Au ball) is formed at a leading end(first end) of the metal wire (such as an Au wire) for wire bonding andconnected (ball-connected) to the first electrode pad 7 of the firstsemiconductor element 5. The connecting step for the metal ball isperformed by applying a load and ultrasonic oscillation in the samemanner as the ordinary wire bonding.

As shown in FIG. 10, after a metal ball 34 which is formed at a leadingend of a metal wire 33 is connected to the electrode pad 7, a bondingtool (capillary) 35 which supports the metal wire 33 is lowered and alsomoved in a direction of the end portion of the semiconductor element 5(a wiring direction of the metal wire 33/a direction toward theconnection pad 4 of the wiring board 2) to contact the metal wire 33with the insulating protection film 8 which is disposed on the peripheryof the electrode pad 7. The metal wire 33 is contacted to the insulatingprotection film 8 continuously from the portion connected to theelectrode pad 7. Thus, the height of the metal wire 33 on thesemiconductor element 5 applying forward bonding can be lowered.

The operation of contacting the metal wire 33 to the insulatingprotection film 8 may be performed together with the metal ballsquashing operation as shown in FIG. 11 and FIG. 12. In other words, themetal ball 34 formed at the leasing end of the metal wire 33 isconnected to the electrode pad 7 by pressure bonding as shown in FIG.11, the bonding tool 35 is pressed against the vicinity of the top ofthe metal ball 34, and the metal ball 34 is squashed together with apart of the metal wire 33 to lower the connection height.

Then, as shown in FIG. 12, the bonding tool 35 is lowered and also movedin a direction (wiring direction of the metal wire 33) of the end of thesemiconductor element 5 to contact the metal wire 33 to the insulatingprotection film 8 which is disposed on the periphery of the electrodepad 7. The connection portion between the metal wire 33 and theelectrode pad 7 is squashed, and the squashed portion is continuouslycontacted to the insulating protection film 8. The above operation canbe applied to make it possible to lower the connection height of themetal ball 34 and the height of the metal wire 33 on the semiconductorelement 5.

After the above-described step (including the contacting step of themetal wire 33 to the insulating protection film 8) of connecting themetal ball 34 to the electrode pad 7 is performed, the metal wire 33 islet out from the bonding tool 35 to perform wiring, and the bonding tool35 is simultaneously moved onto the connection pad 4 of the wiring board2. After the metal wire 33 is stitch-bonded to the connection pad 4, thebonding tool 35 is pulled up to cut off the metal wire 33. Thus, thefirst metal wire 31 is formed to electrically connect the firstelectrode pad 7 and the connection pad 4.

The height of the first metal wire 31 on the first semiconductor element5 can also be lowered in the second embodiment. Thus, the element-sideend of the first metal wire 31 can be finely buried into the secondadhesive layer 12 which adheres while keeping small the gap between thefirst semiconductor element 5 and the second semiconductor element 11.In other words, the occurrence of an insulation failure or a shortcircuit because of the contact of the first metal wire 31 buried intothe second adhesive layer 12 with the second semiconductor element 11can be prevented, or the occurrence of a connection failure which mightbe caused when the connection portion between the first metal wire 31and the first electrode pad 7 is deformed excessively when the secondsemiconductor element 11 is adhered can be suppressed.

Therefore, the stacked semiconductor device 30 which is made thin byreducing the gap between the first and second semiconductor elements 5,11 can be provided while the occurrence of an insulation failure or ashort circuit because of the contact between the first metal wire 31 andthe second semiconductor element 11 and the occurrence of a connectionfailure due to excessive deformation of the first metal wire 31 areprevented. In other words, the production yield, reliability and thelike of the thin stacked semiconductor device 30 can be enhanced. Forlowering of the height of the first metal wire, the first embodimentapplying the reverse bonding is more effective.

The present invention is not limited to the above-described embodimentsbut can be applied to the stacked semiconductor devices having varioustypes of structures that the plural semiconductor elements are stackedon the circuit substrate and the wire bonding is applied for connectionof the circuit substrate and the semiconductor element. Such a stackedsemiconductor device and a method of manufacturing it are also includedin the present invention. The embodiments of the invention can beexpanded or modified within the scope of technical idea of theinvention, and the expanded and modified embodiments are also includedin the technical scope of the invention.

1. A stacked semiconductor device, comprising: a circuit substratehaving an element mounting section and a connection portion; a firstsemiconductor element, mounted on the element mounting section of thecircuit substrate, including a semiconductor element body, a firstelectrode pad disposed on a surface of the semiconductor element bodyand an insulating protection film covering the surface while exposingthe first electrode pad; a second semiconductor element, stacked on thefirst semiconductor element via a spacer layer, including asemiconductor element body and a second electrode pad disposed on asurface of the semiconductor element body; a first metal wire whichelectrically connects the connection portion of the circuit substrateand the first electrode pad of the first semiconductor element, thefirst metal wire disposing to contact a vicinity of its end portionconnected to the first electrode pad with the insulating protectionfilm; and a second metal wire which electrically connects the connectionportion of the circuit substrate and the second electrode pad of thesecond semiconductor element.
 2. The device according to claim 1,wherein the spacer layer includes an insulating adhesive layer, and theend portion of the first metal wire is buried in the insulating adhesivelayer.
 3. The device according to claim 1, wherein a first end portionof the first metal wire is ball-connected to the connection portion ofthe circuit substrate, and a second end portion of the first metal wireis connected to a metal bump formed on the first electrode pad of thefirst semiconductor element.
 4. The device according to claim 3, whereinthe second end portion of the first metal wire is connected to the metalbump continuously from a portion contacted to the insulating protectionfilm.
 5. The device according to claim 3, wherein the metal bump issquashed to incline toward an end of the first semiconductor elementwhich is positioned below the first metal wire.
 6. The device accordingto claim 1, wherein a first end portion of the first metal wire isball-connected to the first electrode pad of the first semiconductorelement, and a second end portion of the first metal wire is connectedto the connection portion of the circuit substrate.
 7. The deviceaccording to claim 6, wherein the first metal wire is in contact withthe insulating protection film continuously from the first end portion.8. The device according to claim 6, wherein the first end portion of thefirst metal wire is squashed, and the first metal wire is in contactwith the insulating protection film continuously from the squashedportion.
 9. The device according to claim 1, wherein the circuitsubstrate is provided with a wiring board which has a connection pad asthe connection portion.
 10. The device according to claim 1, wherein thecircuit substrate is provided with a lead frame which has a lead portionas the connection portion.
 11. A manufacturing method of a stackedsemiconductor device, comprising: mounting a first semiconductor elementhaving an electrode pad on an element mounting section of a circuitsubstrate having a connection portion; forming a metal bump on theelectrode pad of the first semiconductor element; connecting a metalball formed at a first end portion of a metal wire to the connectionportion of the circuit substrate by pressure bonding; wiring the metalwire toward the electrode pad of the first semiconductor element;connecting a second end portion of the metal wire to the metal bumpformed on the electrode pad while contacting the metal wire to aninsulating protection film which is formed to cover a periphery of theelectrode pad; and stacking a second semiconductor element on the firstsemiconductor element via a spacer layer.
 12. The manufacturing methodaccording to claim 11, wherein the forming the metal bump includessquashing the metal bump to incline toward the feeding direction of themetal wire.
 13. The manufacturing method according to claim 11, whereinthe connecting the metal wire to the metal bump includes connecting thesecond end portion of the metal wire to the metal bump continuously fromthe portion contacted to the insulating protection film.
 14. Themanufacturing method according to claim 13, wherein the connecting themetal wire to the metal bump includes squashing the metal bump to whichthe metal wire is connected.
 15. The manufacturing method according toclaim 11, wherein the connecting the metal wire to the metal bumpincludes pressing the metal wire to the insulating protection film afterthe second end portion of the metal wire is connected to the metal bump.16. The manufacturing method according to claim 11, wherein the spacerlayer includes an insulating adhesive layer, and the second end portionof the metal wire is buried in the insulating adhesive layer.
 17. Amanufacturing method of a stacked semiconductor device, comprising:mounting a first semiconductor element having an electrode pad on anelement mounting section of a circuit substrate having a connectionportion; connecting a metal ball formed at a first end portion of ametal wire to the electrode pad of the first semiconductor element bypressure bonding; wiring the metal wire toward the connection portion ofthe circuit substrate while contacting the metal wire to an insulatingprotection film which is formed to cover a periphery of the electrodepad; connecting a second end portion of the metal wire to the connectionportion of the circuit substrate; and stacking a second semiconductorelement on the first semiconductor element via a spacer layer.
 18. Themanufacturing method according to claim 17, wherein the wiring the metalwire includes contacting the metal wire to the insulating protectionfilm continuously from the portion connected to the electrode pad. 19.The manufacturing method according to claim 17, wherein the connectingthe metal wire to the electrode pad includes squashing the metal ballwhich is connected to the electrode pad.
 20. The manufacturing methodaccording to claim 17, wherein the spacer layer includes an insulatingadhesive layer, and the first end portion of the metal wire is buried inthe insulating adhesive layer.